Facilitation of cancer metastases by an air pollutant

An experimental model was designed to test the possibility that inhalation of a noxious air pollutant may facilitate the blood-borne cancer cell metastasis to the lungs. Animals were exposed to inhalation of air containing 0.8 ppm of nitrogen dioxide for 12 weeks. After this period, animals were infused intravenously with melanoma cells, and 3 weeks later lungs were examined for metastases. The results indicate that NO2exposed animals develop significantly higher number of lung metastases (P less than 0.0025) than the controls. Such results raise the possibility that the inhalation of NO2 from ambient air may facilitate the seeding and proliferation of blood-borne cancer cells in the human lung.